Continuous mixer with screw discharge control

ABSTRACT

An internal mixer with parallel mixing rotors and a screw controlled discharge. The material discharge rate is controlled by operation of a screw in a conduit from the mixing chamber through which mixed material is discharged. Preferably, the screw is a part of a screw-type extruder and further conditions and extrudes the material.

United States Patent Matsuoka et al.

[54] CONTINUOUS MIXER WITH SCREW DISCHARGE CONTROL [72] Inventors: JamesT. Matsuoka, Brecksvil1e;Ar-

mindo Cantarutti, Akron, both of Ohio [73] Assignee: IntercoleAutomation, Inc., Cleveland, Ohio [22] Filed: July 14, 1969 [21] Appl.No.: 841,349

[52] US. Cl. ..425/208, 425/ 144, 259/192 [51] Int. Cl. ..B29f 3/02 [58]Field of Search ..259/6, 7, 9, 10, 25, 26, 41,

259/42, 45, 46, 192; 18/2 HA, 2 EP; 264/40;

[56] References Cited UNITED STATES PATENTS 3,154,808 11/1964 Ahlefeld,Jr. et a1 ..18/2 EP 3,111,707 11/1963 Buckley ..18/2 HA 51 Oct. 24, 19729/ 1964 Spencer ..18/2 HA 3,447,201 6/1969 Seanor et al. ..18/2 HA2,868,517 1l/l959 Lasch ..259/6 3,023,455 3/ 1962 Geier et al. ..259/9 X3,333,828 8/1967 Boehme ..259/9 3,343,922 9/ 1967 Zimmer et a1. .257/6 X3,348,815 10/1967 Edick ..259/6 3,387,826 6/1968 Loomans ..259/63,505,085 4/1970 Straughn; et a1 ..259/9 X Primary Examiner-Andrew V.Kundrat Attorney-Watts, Hoffmann, Fisher & Heinke [57] ABSTRACT Aninternal mixer with parallel mixing rotors and a screw controlleddischarge. The material discharge rate is controlled by operation of ascrew in a conduit from the mixing chamber through which mixed materialis discharged. Preferably, the screw is a part of a screw-type extruderand further conditions and extrudes the material.

18 Claims, 9 Drawing Figures CONTINUOUS MIXER WITH SCREW DISCHARGECONTROL FIELD OF THE INVENTION This invention relates to a internalmixer for mixing materials such as rubber, plastic and the like, andmore particularly to a continuous mixer with twin rotors and ascrew-controlled discharge.

PRIOR ART Internal mixers for continuously mixing materials within achamber by the action of parallel rotors are known as exemplified in US.Pat. No. 3,154,808.

SUMMARY OF THE INVENTION The present invention comprises improvedmethods of and apparatus for establishing desired mixing conditions in acontinuous mixer by positively conveying at a controlled rate mixedmaterial from the mixing chamber. In accordance with this invention arotated screw in a discharge conduit controls the rate of discharge bythe speed of screw rotation. Advantageously, the screw also functions asan extruder rotor to further condition and extrude the material throughan extrusion die.

In a preferred embodiment of this invention, a continuous mixer isprovided with two parallel bladed rotors in longitudinally communicatingside-by-side cylindrical portions of a mixing chamber, with an inlet atone end of the chamber and an outlet at the other. The mixing blades ofthe rotors are constructed to move material back and forth within thechamber during mixing. Material throughflow rate is determined by therate at which the discharge screw is rotated.

Each rotor includes, in axial relationship, a screw input or materialfeeding portion, a central mixing portion with blade portions that twistin opposite directions to mix material within the portion of thecylindrical chambers, and a screw output portion in the output portionof the cylindrical chambers just beyond the mixing chamber. The screwoutput portion in part helps to advance mixed material to the dischargeopening, and serves to dampen pulsating load requirements on the rotordrive, characteristic of bladed mixers.

Each rotor is formed with what would be considered a central, generallycylindrical, body portion, and the mixing portion of each rotor hasblades formed in a generally continuous rotor surface. While blades ofvarious construction can be used, it is advantageous and preferred toutilize first and second pairs of blades on the mixing portion of eachrotor extending inward toward the center of the mixing portion, fromopposite ends. The blades of each pair are displaced one from the otherapproximately 180 circumferentially about the rotor, and each pairextends in generally oppositely curved, preferably helical, paths towardthe center of the rotor. Blades of the first pair are displacedperipherally about the rotor from the second pair and the inner ends ofthe blades of the first pair are overlapped axially with respect to theinner ends of the blades of the second pair. Gaps separate the inner endportions of adjacent blades of opposite pairs and extend radially inwardof the rotor to a substantial depth.

At the discharge end of the mixing chamber, a dischargeor output portionof the mixer communicates directly with a discharge conduit, in sealedrelationship. For compactness, the discharge conduit extends at rightangles to the parallel bladed rotors.

A helical discharge screw fits closely within the discharge conduit andhas a small lead relative to its diameter. As a result, the helicalthread of the screw acts as an obstruction to material flow andcontrolled rotation of the screw controls the flow rate of material fromthe mixing chamber. This control the construction of the thread on theoutput portion of each parallel rotor just upstream from the dischargeorifice which does not provide positive displacement, but rather permitthe resistance established at the discharge orifice by the dischargescrew to directly affect the pressure in the mixing chamber.

During mixing, temperatures of the material being mixed are typicallyincreased as a result of mechanical working. With many materials, thetemperature must be maintained below certain levels to prevent, forexample, scorching, deterioration, or other undesirable effects.Temperature control within the mixing chamber and discharge conduit ofthe present invention is provided by drilled passageways in the wallportion of the mixing chamber parallel to the cylindrical portions inwhich the rotors turn, and in the wall portion of the apparatus definingthe discharge conduit. Manifold chambers about the wall portions inwhich the drilled passageways extend circulate heat exchange fluidthrough the drilled passageways and facilitate a relatively high volumeflow of heat exchange fluid closely adjacent the inner wall surfaces.This assures efficient transfer of heat and effectively controls thetemperature of the material being mixed and discharged.

In the preferred embodiment, in which the discharge conduit anddischarge control screw comprise an extruder, important advantagesaccrue by virtue of the integral construction. In such an integral,sealed, unit, the mixed material discharge from the continuous mixer isnot subjected to contact with contaminants or with an oxidizingatmosphere as it otherwise might be during transportation betweensaparated mixers and extruder units. In addition, direct transferconserves the heat normally lost in transporting material to an extruderremote from the mixer and the extruder can be somewhat smaller in size,since it is not necessary to heat the material an appreciable extentwithin the extruder. The typical initial working section of aconventional extruder can be omitted and only what are referred to asthe transition section and metering section are required in thiscombination. It will readily be apparent that substantial savings inpower consumption also result.

As a result of the above and other features, the present inventionprovides new and improved methods of and apparatus for continuouslymixing materials such as rubber, plastic and the like. A general objectof the present invention, then, is to provide a continuous internalmixing machine with two cylindrical chambers having charging anddischarging openings to permit the continuous flow of material, twocounter-rotating bladed rotors that mix material within the mixingchamber substantially without forcing the material from the chamber, ascrew discharge control in a conduit for receiving material flowingthrough the mixing chamber, and means to rotate the discharge screw at ais facilitated by I controlled speed to convey material away from thedischarge opening of the mixing chamber and control the flow of materialtherethrough.

Another object of this invention is to provide a continuous internalmixing machine as in the preceding object, in which the through flow ofmaterial in the mixing chamber is controlled by an extruder thatdirectly receives material from the discharge opening and which-therebyprovides an improved, efficient and integrated operation.

A further object of this invention is to provide improved methods ofcontinuously mixing material such as rubber, plastics and the like, inwhich mixed material is continuously discharged by positive displacementat a rate independent of the pressure in the mixing chamber.

These and other objects, features and advantages of this invention willbecome more apparent as the invention becomes better understood from thefollowing detailed description, when considered in connection with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of a continuousinternal mixing machine with a screw controlled discharge in the form ofan extruder, embodying the present invention;

FIG. 2 is a front elevational view of the apparatus of FIG. 1, withparts removed and parts in section;

FIGS. 3 and 3A are, together, a longitudinal sectional view of thecontinuous mixer shown in FIG. 1, taken along the line 3-3A;

FIG. 4 is a longitudinal sectional view of the discharge controlextruder of FIGS. 1 and 3A, taken along the Iine4-4;

FIG. 5 is a partial sectional view of the cooling chamber manifold forthe mixing chamber, taken along the line 5-5 of FIG. 1;

FIG. 6 is a sectional view of a portion of the cooling chamber manifold,taken along the line 6-6 of FIG. 5;

FIG. 7 is a partial plan view on an enlarged scale of the internalmixing machine as shown in FIG. 1, with parts removed and parts brokenaway to show the rotors within the continuous mixer; and

FIG. 8 is a sectional view of a rotor taken through the mixing chamberalong the line 8-8 of FIG. 3A.

DESCRIPTION OF A PREFERRED EMBODIMENT With reference to the drawings,and particularly FIG. 1, a continuous internal mixer embodying thepresent invention ,is indicated generally by reference character A andincludes an elongated mixer subassembly B, an extruder subassembly Cintegrally connected to the mixer subassembly and extending transverselythereof, and a common base D supporting the mixer and extrudersubassemblies. Rotors of the mixer subassembly B are driven by a mixerdrive E through a gear reducer R. Materials such as rubber, plastic andthe like are mixed in subassembly B and discharged directly to theextruder subassembly C. A drive G operates the extruder subassembly Cthrough a gear reducer H. The extruder subassembly C controls thethrough rate of material being mixed within the mixer subassembly, andfurther works and extrudes material received from the mixer subassembly.

The mixer subassembly B includes a mixing chamber 10 with side-by-side,longitudinally communicating, generally cylindrical chamber portions10a, 10b, the chamber 10a being shown in FIGS. 3 and 3A and the chamber10b being a mirror image thereof, and shown in FIG. 5. The mixer has aproduct inlet opening at one end, indicated generally at 12, in a feedhopper housing or assembly 14 that communicates with both chamberportions 10a, 10b and which opens upward. A product discharge opening 16communicates with the chamber portions 10a, 10b at the opposite end ofthe mixer and opens downward. Two rotors 18a, 18b extend through themixing chamber 10, in side-by-side relationship, one in each generallycylindrical chamber portion 10a, 10b, and are driven in counter rotationby the mixer drive through the reducer R. The rotors each extend beyondthe mixing chamber, into the feed hopper at one end and over thedischarge opening at the other end.

As best shown in FIGS. 1, 3, 3A and 5, the mixing chamber 10 is formedby a cast housing 20 with a curved wall-forming portion 22 providinggenerally cylindrical internal surfaces that define the mixing chamberpart of the chamber portions 10a, 10b. The housing is splithorizontally, with upper and lower portions 20a 20b being securedtogether along horizontal flanges by cap screws 23 (see FIG. 1). Thecast housing 20 terminates at opposite ends in flanges 25, 26 with flatend faces 25a, 26a. Parallel longitudinally extending drilled passages28 are reformed within the wall 22 formed by each portion 20a, 20b ofthe housing 20, closely adjacent the inner forming surface. An open endof each passage 28 is closed by a plug 29. Outer manifold chambers 30are formed on opposite lateral sides of the mixing chamber for thecirculation of heat transfer fluid through the drilled passages 28. Asbest understood from FIG. 5, considered with FIGS. 3 and 3A, on eachlateral side of the mixing chamber the upper housing 20a and lowerhousing 20b are divided longitudinally into inlet and outlet chambers bya vertical flange 34 that abuts outer plates 36, which are secured tothe end flanges 25, 26, spaced from the wall 22. An axially extendingdivider wall 38 along the upper housing 20a, and a divider wall 39 alongthe lower housing 20b, further divide the inlet and outlet chambermanifolds to control the flow of heat transfer fluid through theplurality of drilled passages 28. Thus, two inlet manifold chambers 30a,30b are provided in the upper housing 200 between the end flange 26 andthe central flange 34. Two discharge manifold chambers, one of which isshown at 300 in FIG. 3, and which correspond to the inlet manifoldchambers 30a, 30b are located between the central flange 34 and the endflange 25 of the cast housing section 20a. The lower housing section 20bis similarly divided into two inlet chamber manifolds 30e, 30f betweenthe end flange 26 and central flange 34, and two discharge manifoldchambers, one of which is shown at 30g in FIG. 3, between the centralflange 34 and end flange 25, corresponding to the inlet manifoldchambers 30e, 30f. The longitudinally extending drilled passages 28communicate with the manifolds through apertures 40 at the inlet endsand 41 at the outlet ends.

A distributor manifold 44 (FIGS. 1, 5 and 6) is secured to each side ofthe cast housing 20 and has two longitudinally spaced verticallydisposed passages 46, 47 which, respectively, supply fluid to andexhaust'fluid from the manifold chambers 30 through transverse passages48, 49, which communicate with connecting passages 48a, 49a in thehousing 20. One pair of transverse passages 48, 49 is associated witheach manifold chamber 30. The respective outlet transverse passage 49from each manifold section 30 includes a manifold valve 50 forcontrolling the flow of fluid. The vertical passages 46, 47 have ports52 which connect to conduits (not shown) for supplying and exhaustingheat transfer fluid to the distributor manifold 44.

The feed hopper 14 at the input end of the mixing chamber is a casthousing with a peripheral wall 52 that forms a chamber 54 with bottomand side cylindrically curved portions that are parts of the chamberportions a, 10b. The cast housing forms the inlet 12 to the chamberportions 10a, 10b, and has an end face 56 that abuts the end face 25a ofthe housing 20, an opposite end face 58 against which a bearing spider60 is secured with cap screws 62 for supporting one end of the rotors18, and an upwardly opening passageway 64 at the top of the machine. Thelower portion of the hopper 14 includes a wall 66 that forms a jacketwith longitudinally spaced transversely extending end walls 67, 68. Acentral divider wall 69 divides the jacket into an inlet chamber 70 andan outlet chamber 71 which communicate by passages (not shown) throughthe dividing wall 69. Conduits (not shown) supply and withdraw heattransfer fluid from the chambers.

The discharge opening 16 is formed by a cast housing 76 attached to themixer housing 20 by cap screws at the end opposite from the feed hopper.The housing 76 has two longitudinally extending cylindrical chambers 78,79 (see FIG. 4) that form parts of the chamber portions 10a, 10b.Opposite ends of the housing 76 have radial flanges 80, 81. The flange80 abuts the end face 26a of the mixing chamber housing 20 and theopposite flange 81 abuts a fixed bearing housing 84. The flange 81 isdetachably secured against the fixed bearing housing 84 by clamps 86, 87(FIG. 1) and is maintained in alignment by locating dowels (not shown).This construction permits the hopper, mixing chamber and dischargehousings to be moved as a unit relative to the rotors and extrudersubassembly for cleaning or repair. For this purpose, the feed hopper,mixing chamber and discharge housings are supported on an auxiliary base90 for sliding movement on parallel ways 92 on the main base D. Movementis facilitated by a hand crank 94 that drives a pinion 95 carried by theauxiliary base 90. The pinion 95 cooperates with a rack 96 along theways 92 and permits the auxiliary base and supported housings to bemoved from the position shown in solid in FIG. 2 to the position shownin phantom.

Drilled cooling passages 98 extend longitudinally through the housing76, close to and radially spaced about the major portion of thecylindrical chambers 78, 79 for the circulation of heat transfer fluid.Two manifold chambers 99a and 99b are provided about the housing 76adjacent opposite ends of the passages 98 on each lateral side of thehousing 76. The chambers are formed between the end flanges 80, 81 by acentral radial flange 100 and a cover plate 102 welded to the casting.The manifold chambers 99a on each lateral side of the housing 76 areseparated by a central longitudinal flange 104 (FIG. 4). A manifold 106has an discharge conduit 108 and two passages 110, 111 extendingtherefrom and communicating to the manifold chambers 99a. The manifoldhas an inlet conduit 114 that communicates through passages on theopposite side of the radial flange 100, to the manifold chambers 99b.One of such passages is shown at 116 in FIG. 3A. Flow is introduced tothe manifold chambers 99b through the passages 116. Fluid from themanifold chambers 99b flows through drilled ports 120 in the housing tothe drilled passages 98, and flows from the drilled passages 98 throughdrilled ports 121 to the manifold chambers 99a, and thence through thepassages 110, 111 to the manifold 106. Flow is controlledby valves 118in these passages. The manifold 106 is connected to an inlet conduit 122and a discharge conduit 123 which supply and exhaust heat transfer fluidto the manifold.

Both cylindrical chambers 78, 79 communicate with a common opening 125in the bottom of the housing 76. The opening 125, in turn communicatesdirectly with the extruder subassembly C. lBores 128, 129 in the centralupper portion of the housing 76 are provided to receive thermocouplesfor sensing the temperature of material within the chambers 78, 79.

The rotors 18a, 18b extend through the mixing chamber, feed hopperanddischarge housings and extend at opposite ends beyond the feed hopper,and discharge housings. The extending ends are joumaled adjacent thefeed housings 14 in bearing assembles 132 each supported by a spider 60,and adjacent the discharge housing 76 by fixed, aligned, bearingassemblies 134, 136. An adaptor assembly is attached to the end of eachrotor 18a, 18b adjacent the bearing housing 132 and is coupled to arotary union 142, through which heat transfer fluid is supplied (asindicated by the flow arrows in FIG. 3) via a central pipe 143 to acentral cavity 144 of the associated rotor and thence back through therotary union The opposite ends of the rotors 18a, 18b extend beyond thebearing assemblies 134, 136 and each is connected by acoupling 148 to adrive shaft 15001, 150b, respectively, from the gear reducer R.

Both rotors 18a, 18b are shown in FIG. 7 and are of similarconstruction, differing in that the screw threads and blades aretwistedin opposite directions the longer blades are at different endsof the tworotor mixing portions, to provide the desired mixing action with counterrotation. Accordingly, only rotor 18a will be described in detail androtor 18b will be described only to the extent necessary to point outthe differences from rotor 18a.

Rotor 18a may be considered as having a central, generally cylindrical,body, portion 152a with a feeding portion F in the feed hopper 14, acentral mixing portion M in the mixing chamber 10, and an output portion0 in the discharge housing 76. Helical threads 154a, 156a extend fromthe'central body portion 152a and form a double thread screw of uniformlead and thread depth along the feeding portion F of the rotor.

With a double thread screw, material to be mixed is divided and feduniformly to each of two diametrically opposed mixing blades at theinput end of the mixing section of each rotor. Similar helical threads154b, 156b are on the rotor 18b, but twist in the opposite direction.Thus, both feeding portions F advance work product from the feed chamber54 to the mixing chamber 10.

Each helical thread 154a, 156a terminates at a mixing blade of themixing portion M of the rotor 18a. The mixing portion is constructed tothoroughly mix material within the chamber 10, blades of each rotorbeing constructed to act on the material in axially opposed directionsin the mixing chamber. The blades themselves of the two rotors 18a, 18b,by virtue of oppositely twisting portions, have essentially no net screwaction, yet produce a flow of material through the mixing chamber due toa progressive decrease in viscosity of the material from the inlet tothe discharge end of the mixing chamber and hence a lowered resistanceto flow in that direction, resulting from the progressively greaterextent to which material downstream from the inlet has been worked. In apreferred construction shown, four blades are provided on each rotor18a, 18b, and are arranged in pairs at opposite ends of the respectivemixing portions. Thus, the rotor 18a has four blades 160a, 161a, 162a,163a arranged in pairs 160a, 161a and 162a, 163a. The blades of eachpair project from the central rotor body portion 152a in oppositedirections (i.e., are 180 apart in a transverse plane). The pair ofblades 160a, 161a is located at the feed end of the mixing portion M ofthe rotor and the pair of blades 162a, 1630 is at the discharge end.Each blade of a pair curves or twists about the rotor body, preferablyhelically, from an end of the mixing portion toward the center, in thesame direction as the other blade of the pair. The blades of one pair,however, twist or curve in an opposite direction about the rotor fromthe other pair, so that both pairs twist away from the direction ofrotor rotation, considered in the direction from the opposite ends ofthe rotor toward the center of the mixing portion. The blades of onepair are displaced angularly from the blades of the other so that innerends are peripherally spaced. Preferably the lengths of the blades aresuch that the inner ends overlap axially of the rotor. Thus, in theembodiment shown, the blades 160a, 161a are longer than the blades 162a,163a, with the inner ends located beyond the center of the mixingportion M, toward the output portion 0. Preferably, the inner ends ofthe blades 162a, 163a are also located to the same side of the center ofthe mixing portion as the inner ends of blades 160a, 161a. The angulardisplacement between the inner ends of adjacent blades provides gapsthrough which material being mixed can back-flow for remixing. The gapsextend radially inward to a depth that approximately corresponds to theperipheral extent of the basic cylindrical rotor body portion 152a. Arotor with four mixing blades of this general construction is disclosedin somewhat more detail in the copending application of James T.Matsuoka, entitled Continuous Mixer, Ser. No. 758,195, filed Sept. 5,1968, US. Pat. No. 3,565,403 and assigned to the assignee of thisapplication, which disclosure is hereby incorporated herein byreference.

All the blades 160a-163a have a uniform angle, which is typically about30 to 36 with reference to the axis of the rotor and can have a maximumangular displacement peripherally of the rotor body at the respectiveinner ends of adjacent blades 160a, 162a and 161a,

All

163a (and also at corresponding blade portions considered from the innerends outward) of Preferably, the angular displacement is at least 20.Each of the blades 160a-163a shown are of uniform cross sectionthroughout their length, extend about 90 circumferentially about therotor and each has a convex leading surface 160a'-163a' and a concavetrailing surface 160a163a" (see FIG. 8).

Blades 160b, 161b, 162b, 163b are provided on the rotor 18b. In additionto twisting in an opposite direction from the blades l60al63a, theshorter blades 162b, 163b are adjacent the feeding portion F of therotor, beside the longer blades 160a, 161a of the rotor 18a.

The material output portion 0 of the rotor 18a includes a double screwformed by helical threads 166a, 167a extending radially from a taperedbody portion 168a. The helical screw blade 166a joins the mixing thread162a at the juncture of the mixing portion M of the rotor, and thehelical screw thread 167a joins the mixing blade 163. The tapered bodyportion 168a enlarges in cross section in the axial direction ofmaterial flow within the chamber 78 of the housing 76, therebyprogressively diminishing the effective volume of the chamber 78. Thescrew diameter of the output portion 0 is somewhat smaller than that ofthe mixing threads 160a-163a, so that a significant clearance CL existsbetween the peripheries of the blades and the inner wall of the chamber78. This clearance permits a backflow of material relative to forwardscrew action of the helical blades threads 166a, 167a, so that rotationof the rotor does not necessarily effect positive displacement ofmaterial in the chamber 78. The output portion 0 0f the rotor terminatesin an end shroud 169a that closes the end of the chamber 78, just beyondthe opening in the housing 76 that communicates to the extrudersubassembly C. Helical threads 166b, 167b of the rotor 18b twist in anopposite direction from the threads 166a, 167a, and join the longermixing blades b, l6lb rather than the shorter. They are received in thechamber 79 next to chamber 78 and displace material through the opening125 common to the chambers 78, 79.

The extruder subassembly C is comprised of a barrel 171 with acylindrical chamber or conduit 172, a rotor or screw 174 within thechamber 172, the drive G connected to the rotor 174 and controllable tovary the speed of the rotor, and a die assembly 176 at the discharge endof the barrel. The barrel 171 extends transversely of the mixing chambersubassembly, is supported on the common base D, and includes a feedsection and extrusion section (i.e., a pressure and metering section),as shown in FIG. 4.

The feed section of the extruder is formed of a generally cylindricalhousing 180 carried by the support base D, with a central cylindricalpassage 182 forming a part of the barrel chamber 172. An upper surface184 of the housing 180 is fiat and recessed to receive the dischargehousing 76. A generally central, circular opening 186 in the uppersurface of the housing 180 is located directly beneath the opening 125in the discharge housing 76.

Radial flanges 188, 189 are at opposite ends of the feed section housing180 and carry screw clamp assemblies 190, 191 at upper portions tosecure the extruder feed housing 180 and the mixer discharge housing 76together, sealed about the aligned openings 125, 186. The end flange 189abuts and is secured to an adaptor 194 on the gear reducer H. The otherflange 188 abuts and is secured to the extrusion section of the barrel.171.

Drilled passages 196 extend longitudinally through the housing 180,adjacent the inner wall of the central cylindrical passage 182. Thedrilled passages "manifold chambers 199 and the opposite end of adrilled passage. Heat exchange fluid is introduced to the inlet manifoldchamber 198 and is withdrawn from the discharge manifold chamber 199through pipe couplings and conduits (not shown). A vertical bore 204extends through the lower wall of the housing 180 directly beneath theopening 186 to receive a thermocouple for sensing the temperature ofmaterial discharged from the mixer.

The extrusion section of the barrel 171 includes a cylindrical barrelportion 205 with radial flanges 208, 209 at opposite ends. The flange208 is secured to the flange 188 of the feed section housing by suitablecap screws 210 and the flange 209 abuts against and serves to secure thedie assembly 176, which preferably is secured by a hinge 212 at one sideto the flange 209 and is secured at the other side by a screw clamp 213or the like (see FlG. 1). The barrel portion 205 has two temperaturecontrolled zones provided by a plurality of axially extending,peripherally spaced, drilled passages 215 within the barrel walladjacent the flange 208, and a plurality of similar drilled passages 216adjacent the flange 209. Inlet and exhaust manifold chambers'218, 219for passages 215 are formed between spaced radial flanges 220, 221 andbetween flange 221 and flange 208, by cover plates 222, 223. Fluid issupplied to the chamber 218 and exhausted from the chamber 219 throughpipe fittings 224, 225 and flows from the chamber 218 to each passageway215 through an associated aperture 226, and from the passages215 to theexhaust manifold chamber 219 through an aperture 227. In a similarmanner, heat transfer fluid is circulated through the drilled passages216 from an inlet chamber 228 and an exhaust chamber 229 about thebarrel formed, respectively, between flanges 220 and 230 and between theflange 230 and the end flange 209, by cover plates 232, 233. Fluid isintroduced to the chamber 228 and exhausted form the chamber 229 throughpipe fittings 234, 235 and flows from the inlet chamber 228 to eachdrilled passage 216 through an associated aperture 236 and from thedrilled passages 216 to the discharge chamber 229 through apertures l 5jacent the die assembly 237. Maximum heat transfer is achieved bylocating the pipe fittings 224, 225 and 234, 235 adjacent the centraldividing flange 221 or 230 so that heat transfer fluid circulates acrossthe outer surface of the barrel 205 as well as through the drilledpassages in the barrel wall. Bores 240, 241, 242 are provided atintervals along the length of the extruder barrel in the extrusionsection for thermocouples and/or pressure sensors to monitor conditionsof the material being extruded. Two similar bores 243 are provided inthe die assembly 176 to receive pressure sensors for monitoring thepressure of the material within the die at two spaced locations acrossthe width of the die.

The rotor or screw 174 of the extruder has a nonthreaded portion 174athat extends rearwardly from the barrel through the adaptor 194 andwhich is keyed to a driven gear of the gear reducer H. The opposite endof the rotor terminates adjacent the die assembly 176. A central bore245 extends the length of the rotor, open at the extending end andclosed at the end ad- 176 by a plug 246. A feed pipe 248 is received inthe open end of the bore and extends inward to a location adjacent theplug 246. A return pipe 249 extends from the open end of the centralbore and surrounds the feed pipe 248, to provide a conduit for theoutflow of heat transfer fluid supplied by the feed pipe 248 to thecentral cavity 245. Fluid is supplied and exhausted through a rotaryunion 250 (FIG. 1) connected to the outer ends of the pipes 248, 249.

A continuous helical thread 252 extends from a central body portion 254of the extruder rotor 174 from a radial shroud 256 located just behindthe inlet opening 186, to the end of the rotor adjacent the die assembly176. The thread 252 is preferably of uniform pitch throughout itslength, as shown, but alternatively can be of other conventional ormodified design. The central body portion 254 is of uniform crosssection in the extrusion section of the barrel 171, and is tapered inthe feed section to gradually increase in cross section from the shroud256 toward the extrusion section, thereby providing a graduallydecreasing volume available to material progressing from the opening 186to the extrusion section of the barrel 171. A screw collar 258 and seal259 in addition to the shroud 256 close the rear end of the barrelchamber 172.

In operation, material to be mixed is introduced through the inlet 12provided by the opening 64 to the feed hopper 14. The material isreceived by the feed portions F of the two counter rotating rotors 18a,18b, which are driven at a suitable speed by the mixer drive E. Underproper operating conditions, the feed portions F advance the material tothe mixing portions M of the rotors within the mixing chamber 10 understarved conditions. As material is continually fed to the mixing chamber10, the blades of the mixing section M of each rotor work the materialwithin the mixing chamber in a generally back and forth direction byvirtue of the oppositely twisting blades on each rotor. In addition, theblades spread the material within the chamber against the inside surfacethereof and shear the material between the blades and the chamber wall,The peripherally displaced inner ends of the blades of each rotor, byvirtue of the axially overlapping relationship, permit a limited flow ofmaterial through the gaps between the inner ends so that the materialwill in part flow in a tortuous mixing path as it is worked by theblades. This provides an intermixing of the material on opposite sidesof the blades.

Material being mixed within the mixing chamber progressively decreasesin viscosity and, when opposed in its movement within the chamber bymore viscous material introduced from the feed hopper and feed screwsand moved forward by the mixing blades adjacent the mixing chamberinlet, flows from the mixing chamber to the chambers 78, 69 in thedischarge housing 76. The work performed on the material in the mixingchamber by the rotors and the energy absorbed by the material and theincrease in temperature thereof depends in part upon the pressure towhich the material is subjected within the mixing chamber. This, inturn, depends upon the rate at which material is introduced to themixing chamber and. the resistance or back pressure established at theoutlet to the mixing chamber.

Material advanced through the mixing chamber to chambers 78, 79 is movedby the helical threads 166, 167 of the output portions of the rotorstoward the ends of the chambers 78, 79 which are blocked by the rotorshrouds 169. The material is discharged transversely through theopenings 125 and 186 to the discharge passage 182 in which the screw orrotor 174 operates. A downward component of force is exerted upon thematerial from the chambers 78, 79 toward the discharge passage 182 byvirtue of the tapered body portions 168 of the output portions 0 of themixing rotors.

The rotor 174 fits closely within the discharge conduit or passage 182,and exerts a very positive control over the flow of materialtherethrough. On the other hand the relatively large clearance gap CLbetween the helical threads 166, 167 of the mixing rotors and thesurrounding chamber walls prevents the output portion 0 of the mixingrotors from producing a positive displacement of material in thechambers 78, 79. As a result, the resistance of the rotor 174 to theoutflow of material is transmitted back to the mixing chamber andaffects the pressure that is developed therein by the rotor action andthe rate of introduction of material to be mixed. The lead or pitch ofthe screw 252 of the rotor 174 is sufficiently small to prevent materialfrom flowing to any significant degree along the screw rotor 174 withoutan accompanying rotation of the screw. Accordingly, the back pressure onthe mixing chamber and the discharge rate are accurately controlled bythe speed of rotation of screw rotor 174 under control of the variablespeed drive motor G by virtue of a positive incremental discharge ofmaterial through the discharge conduit 182 established by the screwrotation.

In a preferred embodiment, as disclosed, the discharge control screwperforms the further function of conditioning and extruding the materialdischarged from the continuous mixer subassembly. Because the materialnever leaves the machine, the direct transfer from the mixer subassemblyto the extruder subassembly eliminates the loss of heat and the chancefor contamination of material that typically accompany the transfer tomaterial from a mixing machine to a separate extruder. Furthermore, theuse of the extruder screw to control the discharge rate of the mixingmachine eliminates the need for a separate control screw or othercontrol mechanism, reducing the parts required. Power requirements arealso reduced because the need for reworking mixed material to raise thematerial to the required temperature after loss of heat that accompaniestransfer to a remote extruder is not necessary.

Rotation of the extruder screw 174 advances material from the feedsection of the screw, which provides a progressively decreased volumefor the material in the barrel as it advances toward the extruder dieassembly 176. The material is advanced to the pressure and meteringsection or extrusion section, where it is forced under pressure throughan extruder die assembly 176.

The temperature of the material being mixed and extruded can becontrolled throughout the machine, by the flow of heat transfer fluidthrough the drilled passages closely adjacent the inside surfaces of thevarious chambers, as already described in detail. The independentcontrol of supply and exhaust of heat transfer fluid to the variouschambers permits maximum temperature control and flexibility toestablish the required temperature at different locations within themachine.

Typically, the temperature of the material being mixed is an indicationof energy absorbed and hence an indication of the intensity of themixing. The mixing intensity is a function of both the rotor speed andthe pressure on the material within the mixing chamber. The temperatureof the material being discharged or the pressure within the mixer can bemeasured by suitable thermocouples or pressure sensors, such as may bepositioned in the bores 128, 129 of the discharge housing 76 to give anindication of the mixing intensity. Thus, the measured temperature ofthe material, being an indication of the mixing intensity, can be usedto indicate whether uniform and adequate mixing takes place. Changes inthe mixing intensity to which the material being mixed and discharged issubjected can be made by adjusting the speed of rotation of thedischarge control screw 174, and this will result in an accompanyingchange in the temperature of the material discharged. Decreased speedsresults in greater mixing intensity and higher discharge temperatures.Such changes can be made manually by an operator after observing thetemperature of the material being discharged or by observing thepressure in the mixing chamber, or can be made automatically through aconventional motor control for the drive motor of the discharge screw,actuated by temperature or pressure sensors. Thus, while the rotorrotation will typically be set to establish a desired intensity ofmixing, adjustments in mixing intensity can be made through control ofthe discharge rate in response to either temperature measurements ofdischarged material or pressure measurements within the mixer.

Controlled rotation of the screw 174 readily and accurately controls thematerial discharge rate virtually independent of typical viscositychanges in the material or of any tendency of the material to adhere tothe discharge passageway. Thus, a slight change in the temperature ofthe material at the discharge and accompanying change in viscosity doesnot immediately affect the rate of discharge flow and hence the pressurewithin the mixing chamber.

Typically, the rotational speed of the discharge screw is correlatedwith the rate of material input to the mixing chamber so that the mixingchamber does not become overloaded with material and interfere with thedesired starved feeding conditions, i.e., the material should not backup into and pack the feeding portions F of the rotors.

been provided in which the material throughput is affected by operationof a screw in a discharge conduit connected to the mixing chamber. Inthe preferred embodiment, the discharge control screw additionallyoperates upon the discharged material to extrude the material through adie, reducing total power requirements, permitting a reduction in theoverall length of the extruder required, and eliminating chances ofcontamination of the mixed material during transfer to the extruder.

' While a preferred embodiment and mode of operation of this inventionhave been described in detail, it will be apparent that variousmodifications or alterations may be made therein, without parting fromthe spirit and scope of the invention.

What is claimed is:

1. In a continuous internal mixer: structure forming a mixing chamberwith a wall portion defining two interconnected substantiallycylindrical parallel portions; two bladed rotors, one in eachcylindrical portion of the mixing chamber and supported for rotationtherein and each having a central portion in the mixing chamber withblade portions orientated more lengthwise of the axis of the rotor thancircumferentially thereof and twisting in opposite directions for mixingmaterial within the chamber; a charging opening to said mixing chamberadjacent one end thereof; a discharge opening from said mixing chamberadjacent an end opposite from the charging opening; means on said rotoradjacent the charging opening for introducing material-into the mixingchamber; structure forming a material receiving conduit, with a wallportion defining a cylindrical passageway, said conduit being adjacentthe mixing chamber in direct communication with said discharge openingfor receiving material advanced under pressure through the mixingchamber and through the discharge opening; a rotatable screw in saidreceiving conduit closely received within the cylindrical portion tocontrol flow of material frommixing chamber into and through theconduit; means to rotate said screw at a controlled rate to conveymaterial away from the discharge opening of the mixing chamber; drilledpassageways in said wall portion defining the substantially cylindricalparallel por' tions of the mixing chamber, extending axially of thecylindrical portions, and manifold chambers about said wall portioncirculating heat exchange fluid through said drilled passageways; anddrilled passageways in said wall portion defining the cylindricalpassageway, extending axially thereof, and manifold chambers about saidlast-mentioned wall portion for circulating heat exchange fluid throughsaid last-mentioned drilled passageways.

2. In a continuous internal mixer: structure forming a mixing chamberhaving two interconnected substantially cylindrical parallel portions;two bladed rotors, one in each cylindrical portion of the mixingchamber, supported for rotation therein and each having a centralportion in the mixing chamber with blade portions orientated morelengthwise of the axis of the rotor than circumferentially thereof andtwisting in opposite directions to mixmaterial in the mixing chamber; afirst opening to said mixing chamber adjacent one end thereofthroughwhich material to be mixed is charged;

second screw portion on each a second opening from said mixing chamberadjacent an end opposite from said first opening through which mixedmaterial is discharged; afirst screw portion on each of said bladedrotors adjacent said first opening adapted'to advance material to saidmixing chamber; a

of said bladed rotors adjacent an opposite end of the rotor from thefirst screw portion and adjacent said second opening, said second screwportions having substantial peripheral clearance relative to asurrounding chamber portion; structure forming a material receivingconduit, at least a portion of which is cylindrical, in communicationwith said second opening for receiving material advanced under pressurethrough the mixing chamber and said second opening; a rotatable screwextending axially in said receiving conduit closely received within thecylindrical portion to control flow of material from the mixing chamberinto and through the conduit; and means to rotate said screw at acontrolled rate to convey mate rial away from said second opening.

' 3. In a continuous internal mixer: structure forming a mixing chamberhaving two interconnected substantially cylindrical parallel portions;two bladed rotors, one in each cylindrical portion of the mixingchamber, supported for rotation therein and each having a centralportion in the mixing chamber with blade portions orientated morelengthwise of the axis of the rotor than circumferentially thereof andtwisting in opposite directions to mix material in the mixing chamber; afirst opening to said mixing chamber adjacent one end thereof throughwhich material to be mixed is charged; a second opening from said mixingchamber adjacent an end opposite from said first opening-through whichmixed material is discharged; a first screw portion on each of saidbladed rotors adjacent said first opening adapted to advance material tothe central bladed portion; a second screw portion on each of saidbladed rotors adjacent said second opening, adapted to aid indischarging material from the mixing chamber said second screw portionshaving substantial peripheral clearance relative to a surroundingchamber portion; structure forming a material receiving conduit, atleast a portion of which is cylindrical, in communication with saidsecond opening for receiving material advanced through the mixingchamber and second opening, and having a discharge end and an extrusiondie at said end; a rotatable screw extending axially in said receivingconduit closely received within the cylindrical portion to control flowof material from the mixing chamber intoand through the conduit, andconstructed to further condition said material through rotation of saidscrew; means to rotate said screw at a controlled rate to conveymaterial away from said second opening and to force said materialaxially along the conduit and through said extrusion die; drilledpassageways in said wall portion defining the substantial cylindricalparallel portions of the mixing chamber, extending axially of thecylindrical portions, and manifold chambers about said wall portion forcirculating heat exchange fluid through said drilled passageways; anddrilled passageways in said wall portion defining the cylindricalportion of said coriduit, extending axially thereof, and manifoldchambers about said last-mentioned wall portion for circulating heatexchange fluid through said last-mentioned drilled passageways.

4. In a continuous internal mixer: structure forming a mixing chamberhaving two interconnected substantially cylindricalparallel portions;two bladed rotors, one in each cylindrical portion of the mixingchamber, supported for rotation therein and each having a centralportion in the mixing chamber with blade portions that twist in oppositedirections to mix material in the mixing chamber, said blade portions ofat least one of said rotors having first and second pairs of bladesformed in a generally continuous rotor surface and extending inward fromadjacent opposite ends of the rotor, the blades of each pair beingdisplaced one from the other approximately 180 circumferentially aboutthe rotor, each pair extending in a generally opposite helical pathtoward the center of the rotor, the blades of the first pair beingdisplaced peripherally about the rotor from the second pair, with theinner ends of the blades of the first pair being overlapped axially withrespect to the inner ends of the blades of the second pair; a firstopening to said mixing chamber adjacent one end thereof through whichmaterial to be mixed is charged; a second opening from said mixingchamber adjacent an end opposite from said first opening through whichmixed material is discharged; a screw feed portion on each of saidbladed rotors adjacent said first opening adapted to advance material tothe central bladed portion; structure forming a material receivingconduit, at least a portion of which is cylindrical, in communicationwith said second opening for receiving material advanced under pressurethrough the mixing chamber and second opening; a rotatable screwextending axially in said receiving conduit closely received within thecylindrical portion and extending substantially the length thereof tocontrol flow of material from the mixing chamber into and through theconduit; and means to rotate said screw at a controlled rate to conveymaterial away from said second opening of the mixing chamber.

5. In a continuous internal mixer: structure forming a mixing chamberhaving two interconnected substantially cylindrical parallel portions;two bladed rotors, one in each cylindrical portion of the mixingchamber, supported for rotation therein and each having a centralportion in the mixing chamber with blade portions that twist in oppositedirections to mix material in the mixing chamber, the bladed portions ofat least one of said rotors having first and second pairs of bladesformed in a generally continuous rotor surface and extending inward fromadjacent opposite ends of the rotor, the blades of each pair beingdisplaced one from the other approximately 180 circumferentially aboutthe rotor, each pair extending in a generally opposite helical pathtoward the center of the rotor, the blades of the first pair beingdisplacedperipherally about the rotor from the second pair, with theinner ends of the blades of the first pair being overlapped axially withrespect to the inner ends of the blades of the second pair; a firstopening to said mixing chamber adjacentone end thereof through whichmaterial to be mixed is charged; a second opening from said mixingchamber adjacent an end opposite from said first opening through whichmixed material is discharged; a first screw portion on each of saidbladed rotors adjacent said first opening adapted to advance material tothe central bladed portion; a second screw portion on each of saidbladed rotors adjacent an opposite end of the rotor from the first screwportion and adjacent said second opening, said second screw portionhaving substantial peripheral clearance relative to a surroundingchamber portion; structure forming a material receiving conduit, atleast a portion of which is cylindrical, in communication with saidsecond opening for receiving material advanced under pressure throughthe mixing chamber and second opening; a rotatable screw extending.axially in said receiving conduit closely received within thecylindrical portion and extending substantially the length thereof tocontrol flow of material from the mixing chamber into and through theconduit; and means to rotate said screw at a controlled rate to conveymaterial away from said second opening of the mixing chamber.

6. In a continuous internal mixer: structure forming a mixing chamberhaving two interconnected substantially cylindrical parallel portions;two bladed rotors, one in each cylindrical portion of the mixingchamber, supported for rotation therein and each having a centralportion in the mixing chamber with blade portions that twist in oppositedirections to mix material in the mixing chamber, the bladed portions ofat least one of said rotors having first and second pairs of bladesformed in a generally continuous rotor surface and extending inward fromadjacent opposite ends of the rotor, the blades of each pair beingdisplaced one from the other approximately circumferentially about therotor, each pair extending in a generally opposite helical path towardthe center of the rotor, the blades of the first pair being displacedperipherally about the rotor from the second pair, with the inner endsof the blades of the first pair being overlapped axially with respect tothe inner ends of the blades of the second pair; a first opening to saidmixing chamber adjacent one end thereof through which material to bemixed is charged; a second opening from said mixing chamber adjacent anend opposite from said first opening through which mixed material isdischarged; a first screw portion on each of said bladed rotors adjacentsaid first opening adapted to advance material to the central bladedportion; a second screw portion on each of said bladed rotors adjacentan opposite end of the rotor from the first screw portion and adjacentsaid second opening, said second screw portions having substantialperipheral clearance relative to a surrounding chamber portion;structure forming a material receiving conduit, at least a portion ofwhich is cylindrical, in communication with said discharge opening forreceiving material advanced under pressure through the mixing chamberand second opening, and having a discharge end and an extrusion die atsaid end; a rotatable screw extending axially in said receiving conduitclosely received within the cylindrical portion and extendingsubstantially the length thereof to restrict flow of material from themixing chamber into and through the conduit and constructed to furthercondition said material through rotation of said screw; means to rotatesaid screw at a controlled rate to convey material away from said secondopening of the mixing chamber and to force said material axially alongthe conduit and through said extrusion die.

7. In a method of continuously mixing material such as rubber, plastics,and the like, the steps comprising:

introducing material to be mixed into a mixing 17 chamber and adjacentone end of a pair of adjacent generally coextensive rotors each havingbladed portions twisting in opposite directions, rotating the rotors inopposite directions to mix the material, continuously advancing thematerial along the rotors toward a discharge passageway from the mixingchamber, restricting movement of material through the dischargepassageway by a material moving means offset from the axes of the rotorsand operative to positively convey material from the dischargepassageway, sensing pressure within the mixing chamber, and varying thespeed of said material moving means to maintain optimum pressure in themixing chamber.

8. In a method of continuously mixing material such as rubber, plastics,and the like, the steps comprising: introducing material to be mixedinto a mixing chamber and adjacent one end of a pair of adjacentgenerally coextensive rotors each having blade portions r thatareoriented more lengthwise of their axis of rotation thancircumferentially and twist in opposite directions, rotating the rotorsin opposite directions to mix the material, continuously advancing thematerial along the rotors into a conduit in anextruder housing whichconduit is connected with the mixing chamber and is radially offset fromand extends transversely of the axis of the rotors, controlling the rateof flow of material from the mixing chamber by controlling thethroughput of the extruder by varying the speed of rotation of anextruder screw in the conduit, and circulating a heat exchange fluidthrough passages in the walls of the mixing chamber and extruder housingto control the temperature of material being mixed.

9. in a method of continuously mixing material such as rubber, plastics,and the like, the steps comprising: introducing material to be mixedinto a mixing chamber and adjacent one end of a pair of adjacentgenerally coextensive rotors, rotating the rotors to mix the materials,advising the material under pressure along the rotors toward a dischargepassageway'from the mixing chamber, restricting movement of materialthrough the discharge passageway while concurrently and positivelyconveying incremental portions of material from the dischargepassageway, sensing the temperature of the material advanced from themixing chamber and establishing a desired temperature by changing therate at which material is conveyed from the discharge passageway.

10. in a continuous internal mixer: a structure forming a mixing chamberhaving two interconnected substantially cylindrical parallel portions;two rotors, one supportedrby bearings adjacent opposite ends thereof forrotation in each cylindrical portion of the mixing chamber and eachhaving in the mixing chamber a central portion with blade portionsoriented more lengthwise of the axis of the rotor than circumferentiallythereof and twisting, in opposite directions less than 180 about theaxis of the rotor to mix materit al in the mixing chamber; each of saidblade portions having convex leading surfaces; said oppositely twistingblade portions of each rotor extending inwardly from adjacent oppositeends of the mixing chamber toward the center of the rotor in generallyhelical paths; means for rotating said rotors in opposite directions;a'first opening to said mixing chamber adjacent one end thereof throughwhich material to be mixed is charged,

and a second opening from said mixing chamber adjacent an end oppositefrom said first opening through which mixed material is discharged; saidsecond opening being located between said bearings; a screw portion oneach of said rotors adjacent said first opening adapted to advancematerial to the central bladed portion of said rotors; structure forminga material receiving conduit, at least a portion of which iscylindrical, in communication with said second opening and radiallyoffset from and extending transversely of the axes of the rotors forreceiving material from said mixing chamber; passages in the structureforming said mixing chamber for the circulation of heat exchange mediumtherethrough; passages. in the structure forming said material receivingconduit for the circulation of heat medium therethrough; a rotatablescrew extending axially in said receiving conduit closely receivedwithin the cylindrical portion to control the flow of material from themixing chamber into and through said conduit; and means to rotate saidscrew at a controlled rate to convey material away from said dischargeopening.

11. In a continuous internal mixer; a structure forming mixingchamberhaving two interconnected substantially cylindrical parallelportions; two rotors, one supported for rotation in each cylindricalportion of the mixing chamber and each having in the mixing chamberblade portions that twist in opposite directions less than about theaxis of the rotor to mix material in the mixing chamber; means forrotating said rotors in opposite directions; a first opening to saidmixing chamber adjacent one end thereof through which material to bemixed is charged and a second opening from said mixing chamber adjacentan end opposite from said first opening through which mixed material isdischarged;a first screw portion on each of said rotors adjacent saidfirst opening adapted to advance material to the central bladed portionof said rotors; a second screw portion on each of said rotors adjacentan opposite end of the rotor from the first screw portion and adjacentsaid second opening, said second screw portion having substantialperipheral clearance relative to a surrounding chamber portion;structure forming a material receiving conduit, at least a portion ofwhich is cylindrical, in communication with said discharge opening andoffset from and extending transversely of the axes of the rotors forreceiving material from said mixing chamber; passages in the structureforming said mixing chamber for the circulation of heat exchange mediumtherethrough; passages in the structure forming said material receivingconduit for the circulation of heat medium therethrough; a rotatablescrew extending axially in said receiving conduit closely receivedwithin the cylindrical portion to control the flow of material from themixing; chamber into and through said conduit; and means to rotate saidscrew at a controlled rate to convey material away from said dischargeopening.

12. In a continuous internal mixer: a structure forming mixing chamberhaving two interconnected sub stantially cylindrical parallel portions;two rotors, one rotatable in each cylindrical portion of the mixingchamber and having blade portions that twist in opposite directions totheir axes of rotation for mixing material in said'mixing chamber; meansforming a first opening to said mixing chamber adjacent one end thereofthrough which material to be mixed is charged; a second opening fromsaid mixing chamber adjacent to the end thereof remote from said firstopening through which mixed material is discharged; means supportingsaid'structure and said rotors for relative movement axially of saidrotors; means for rotating said rotors in opposite directions; meansforming a material receiving conduit in communication with said secondopening and offset from the axes of said rotors; a rotatable screwextending axially in said receiving conduit to control the flow ofmaterial from said mixing chamber into and through said conduit; andmeans to rotate said screw at a controlled rate.

13. In a continuous internal mixer: a structure forming mixing chamberhaving two interconnected substantially cylindrical parallel portions;two rotors, one rotatable in each cylindrical portion of the mixingchamber and having blade portions that twist in opposite directions totheir axes of rotation for mixing material in said mixing chamber; afirst opening to said mixing chamber adjacent one end thereof throughwhich material to be mixed is charged; a second opening from said mixingchamber adjacent to the end thereof remote from said first openingthrough which mixed'material is discharged;'means supporting saidstructure and said rotors for relative movement axially of said rotors;means connected to the ends of said rotors remote from said firstopening for rotating said rotors in opposite directions; means forming amaterial receiving conduit in communication with said second opening andoffset from the axes of said rotors; a rotatable screw extending axiallyin said receiving conduit to control the flow of material from saidmixing chamber into and through said conduit; and means to rotate saidscrew at a controlled rate.

14. in a continuous internal mixer: a structure forming mixing chamberhaving two interconnected substantially cylindrical parallel portionsand a material inlet opening adjacent to one end of the chamber; tworotors one rotatable in each cylindrical portion of the mixing chamberand having blade portions in said cylindrical portions of said mixingchamber that twist in opposite directions to their axes of rotation formixing material in said mixing chamber; a material discharge openingadjacent to the end of said mixing chamber remote from said inletopening through which mixed material is discharged; means supportingsaid structure for movement axially of said rotors; and means connectedto the ends of said rotors remote from said first opening for rotatingsaid rotors in opposite directions; means forming a material receivingconduit in communication with said discharge opening and offset from theaxes of the rotors; a rotatable screw extending axially in saidreceiving conduit to control the flow of material from the mixingchamber into and through the conduit; and means to rotate said screw ata controlled rate.

15. In a continuous internal mixer: a structure forming mixing chamberhaving two interconnected substantially cylindrical parallel portions;two rotors, one rotatable in each cylindrical portion of the mixingchamber and having blade portions that twist in opposite directions totheir axes of rotation for mixing material in said mixing chamber; afirst opening to said mixing chamber adjacent one end thereof throughwhich material to be mixed is charge; a second opening from said mixingchamber adjacent to the end thereof remote from said first openingthrough which mixed material is discharged; means supporting saidstructure and said rotors for relative movement axially of said rotors;drive means for rotating said rotors in opposite directions; meansstationary with respect to said drive means forming a material receivingconduit in communication with said second opening and offset from theaxes of said rotors; a rotatable screw extending axially in saidreceiving conduit to control the flow of material from said mixingchamber into and through said conduit; and means to rotate said screw ata controlled rate.

16. In a continuous internal mixer: structure forming a rrrixing chamberhaving a material feeding opening adjacent one end; a rotor supported bybearings adjacent opposite ends thereof for rotation in said mixingchamber and having in the mixing chamber a central portion with bladeportions orientated more lengthwise of the axis of the rotor thancircumferentially thereof and twisting in opposite directions less thanabout the axis of the rotor for mixing material in said mixing chamber;e'ach of said blade portions having convex leading surfaces; saidoppositely twisting blade portions extending inwardly from adjacentopposite ends of the mixing chamber toward the center of the rotor ingenerally helical paths, means for rotating said rotor at a controlledspeed; structure forming a material conveying conduit, at least aportion of which is cylindrical, adjacent the end of said mixing chamberopposite said material receiving opening in communication with themixing chamber at a location between said bearings and radially offsetfrom and extending transversely of the axis of said mixing chamber; saidstructure forming said mixing chamber having passageways therein for thecirculation of heat exchange medium closely adjacent the interior wallof said mixing chamber; said structure forming said conduit havingpassageways therein for the circulation of heat exchange medium closelyadjacent the interior wall of said conduit; a rotatable screw extendingaxially in said conduit closely received in the cylindrical portion tocontrol flow of material from the mixing chamber into and through theconduit, said screw being rotatably supported in said conduit with itsaxis offset from the axis of said rotor; and means to rotate said screwat a controlled speed to convey material away from the mixing chamber.

17. In a continuous internal mixer: structure forming a mixing chamber;a bladed rotor supported for rotation in said mixing chamber and havingin the mixing chamber first and second pairs of blade portions eachhaving a convex leading surface and each pair extending in generallyopposite helical paths more lengthwise than circumferentially of theaxis of the rotor from opposite ends of the mixing chamber toward thecenter thereof; said mixing chamber having an opening adjacent one endthrough which material to be mixed is fed thereto; a double-thread screwfeed portion on said rotor in advance of said blade portions; each ofsaid double threads of said screw feed portion terminating at andconnected with one of said pair of blade portions adjacent said screwfeed; structure forming a material receiving conduit extendingtransversely of said mixing chamber and in communication with the end ofsaid mixing chamber opposite said opening through which material is fedthereto for receiving mixed material from said mixing chamber; arotatable screw in said receiving conduit with its axis offset from theaxis of said rotor for controlling flow of material from the mixingchamber into and through said conduit; and means to rotate said screw.

18. in a method of continuously mixing materials such as rubber,plastics, and the like, the steps comprising: introducing material to bemixed into one end of a mixing chamber and adjacent one end of a pair ofadjacent generally coextensive rotors rotatable therein and each havingfirst and second pairs of blades, each having a convex leadingsurfaceand each pair extending in generally opposite helical paths morelengthwise than circumferentially of the axis of the rotors fromopposite ends of the mixing chamber towards the center 22 thereof, theblades of each pair being displaced from one another aboutcircumferentially of the rotor and the blades of one pair beingdisplaced circumferentially about the rotor from the other pair withadjacent ends overlapping; rotating the rotors in opposite directions tomix the material and advance it along the rotors to a screw in a conduitcommunicating with the end of the mixing chamber opposite the end intowhich the material isintroduced and offset from and extends transverselyto the axes of the rotors; controlling the rate of flow of material fromthe mixing chamber by controlling the speed of rotation of the screw,and circulating a heat exchange fluid through passages in the walls ofthe mixing chamber and the screw housing to control the temperature ofmaterial being mixed.

1. In a continuous internal mixer: structure forming a mixing chamberwith a wall portion defining two interconnected substantiallycylindrical parallel portions; two bladed rotors, one in eachcylindrical portion of the mixing chamber and supported for rotationtherein and each having a central portion in the mixing chamber withblade portions orientated more lengthwise of the axis of the rotor thancircumferentially thereof and twisting in opposite directions for mixingmaterial within the chamber; a charging opening to said mixing chamberadjacent one end thereof; a discharge opening from said mixing chamberadjacent an end opposite from the charging opening; means on said rotoradjacent the charging opening for introducing material into the mixingchamber; structure forming a material receiving conduit, with a wallportion defining a cylindricAl passageway, said conduit being adjacentthe mixing chamber in direct communication with said discharge openingfor receiving material advanced under pressure through the mixingchamber and through the discharge opening; a rotatable screw in saidreceiving conduit closely received within the cylindrical portion tocontrol flow of material from mixing chamber into and through theconduit; means to rotate said screw at a controlled rate to conveymaterial away from the discharge opening of the mixing chamber; drilledpassageways in said wall portion defining the substantially cylindricalparallel portions of the mixing chamber, extending axially of thecylindrical portions, and manifold chambers about said wall portioncirculating heat exchange fluid through said drilled passageways; anddrilled passageways in said wall portion defining the cylindricalpassageway, extending axially thereof, and manifold chambers about saidlast-mentioned wall portion for circulating heat exchange fluid throughsaid last-mentioned drilled passageways.
 2. In a continuous internalmixer: structure forming a mixing chamber having two interconnectedsubstantially cylindrical parallel portions; two bladed rotors, one ineach cylindrical portion of the mixing chamber, supported for rotationtherein and each having a central portion in the mixing chamber withblade portions orientated more lengthwise of the axis of the rotor thancircumferentially thereof and twisting in opposite directions to mixmaterial in the mixing chamber; a first opening to said mixing chamberadjacent one end thereof through which material to be mixed is charged;a second opening from said mixing chamber adjacent an end opposite fromsaid first opening through which mixed material is discharged; a firstscrew portion on each of said bladed rotors adjacent said first openingadapted to advance material to said mixing chamber; a second screwportion on each of said bladed rotors adjacent an opposite end of therotor from the first screw portion and adjacent said second opening,said second screw portions having substantial peripheral clearancerelative to a surrounding chamber portion; structure forming a materialreceiving conduit, at least a portion of which is cylindrical, incommunication with said second opening for receiving material advancedunder pressure through the mixing chamber and said second opening; arotatable screw extending axially in said receiving conduit closelyreceived within the cylindrical portion to control flow of material fromthe mixing chamber into and through the conduit; and means to rotatesaid screw at a controlled rate to convey material away from said secondopening.
 3. In a continuous internal mixer: structure forming a mixingchamber having two interconnected substantially cylindrical parallelportions; two bladed rotors, one in each cylindrical portion of themixing chamber, supported for rotation therein and each having a centralportion in the mixing chamber with blade portions orientated morelengthwise of the axis of the rotor than circumferentially thereof andtwisting in opposite directions to mix material in the mixing chamber; afirst opening to said mixing chamber adjacent one end thereof throughwhich material to be mixed is charged; a second opening from said mixingchamber adjacent an end opposite from said first opening through whichmixed material is discharged; a first screw portion on each of saidbladed rotors adjacent said first opening adapted to advance material tothe central bladed portion; a second screw portion on each of saidbladed rotors adjacent said second opening, adapted to aid indischarging material from the mixing chamber said second screw portionshaving substantial peripheral clearance relative to a surroundingchamber portion; structure forming a material receiving conduit, atleast a portion of which is cylindrical, in communication with saidsecond opening for receiving material advanced through the mixingchamber and second opening, and having a discharge end and an extrusiondie at said end; a rotatable screw extending axially in said receivingconduit closely received within the cylindrical portion to control flowof material from the mixing chamber into and through the conduit, andconstructed to further condition said material through rotation of saidscrew; means to rotate said screw at a controlled rate to conveymaterial away from said second opening and to force said materialaxially along the conduit and through said extrusion die; drilledpassageways in said wall portion defining the substantial cylindricalparallel portions of the mixing chamber, extending axially of thecylindrical portions, and manifold chambers about said wall portion forcirculating heat exchange fluid through said drilled passageways; anddrilled passageways in said wall portion defining the cylindricalportion of said conduit, extending axially thereof, and manifoldchambers about said last-mentioned wall portion for circulating heatexchange fluid through said last-mentioned drilled passageways.
 4. In acontinuous internal mixer: structure forming a mixing chamber having twointerconnected substantially cylindrical parallel portions; two bladedrotors, one in each cylindrical portion of the mixing chamber, supportedfor rotation therein and each having a central portion in the mixingchamber with blade portions that twist in opposite directions to mixmaterial in the mixing chamber, said blade portions of at least one ofsaid rotors having first and second pairs of blades formed in agenerally continuous rotor surface and extending inward from adjacentopposite ends of the rotor, the blades of each pair being displaced onefrom the other approximately 180* circumferentially about the rotor,each pair extending in a generally opposite helical path toward thecenter of the rotor, the blades of the first pair being displacedperipherally about the rotor from the second pair, with the inner endsof the blades of the first pair being overlapped axially with respect tothe inner ends of the blades of the second pair; a first opening to saidmixing chamber adjacent one end thereof through which material to bemixed is charged; a second opening from said mixing chamber adjacent anend opposite from said first opening through which mixed material isdischarged; a screw feed portion on each of said bladed rotors adjacentsaid first opening adapted to advance material to the central bladedportion; structure forming a material receiving conduit, at least aportion of which is cylindrical, in communication with said secondopening for receiving material advanced under pressure through themixing chamber and second opening; a rotatable screw extending axiallyin said receiving conduit closely received within the cylindricalportion and extending substantially the length thereof to control flowof material from the mixing chamber into and through the conduit; andmeans to rotate said screw at a controlled rate to convey material awayfrom said second opening of the mixing chamber.
 5. In a continuousinternal mixer: structure forming a mixing chamber having twointerconnected substantially cylindrical parallel portions; two bladedrotors, one in each cylindrical portion of the mixing chamber, supportedfor rotation therein and each having a central portion in the mixingchamber with blade portions that twist in opposite directions to mixmaterial in the mixing chamber, the bladed portions of at least one ofsaid rotors having first and second pairs of blades formed in agenerally continuous rotor surface and extending inward from adjacentopposite ends of the rotor, the blades of each pair being displaced onefrom the other approximately 180* circumferentially about the rotor,each pair extending in a generally opposite helical path toward thecenter of the rotor, the blades of the first pair being displacedperipherally about the rotor from the second pair, with the inner endsof the blades of the first pair being Overlapped axially with respect tothe inner ends of the blades of the second pair; a first opening to saidmixing chamber adjacent one end thereof through which material to bemixed is charged; a second opening from said mixing chamber adjacent anend opposite from said first opening through which mixed material isdischarged; a first screw portion on each of said bladed rotors adjacentsaid first opening adapted to advance material to the central bladedportion; a second screw portion on each of said bladed rotors adjacentan opposite end of the rotor from the first screw portion and adjacentsaid second opening, said second screw portion having substantialperipheral clearance relative to a surrounding chamber portion;structure forming a material receiving conduit, at least a portion ofwhich is cylindrical, in communication with said second opening forreceiving material advanced under pressure through the mixing chamberand second opening; a rotatable screw extending axially in saidreceiving conduit closely received within the cylindrical portion andextending substantially the length thereof to control flow of materialfrom the mixing chamber into and through the conduit; and means torotate said screw at a controlled rate to convey material away from saidsecond opening of the mixing chamber.
 6. In a continuous internal mixer:structure forming a mixing chamber having two interconnectedsubstantially cylindrical parallel portions; two bladed rotors, one ineach cylindrical portion of the mixing chamber, supported for rotationtherein and each having a central portion in the mixing chamber withblade portions that twist in opposite directions to mix material in themixing chamber, the bladed portions of at least one of said rotorshaving first and second pairs of blades formed in a generally continuousrotor surface and extending inward from adjacent opposite ends of therotor, the blades of each pair being displaced one from the otherapproximately 180* circumferentially about the rotor, each pairextending in a generally opposite helical path toward the center of therotor, the blades of the first pair being displaced peripherally aboutthe rotor from the second pair, with the inner ends of the blades of thefirst pair being overlapped axially with respect to the inner ends ofthe blades of the second pair; a first opening to said mixing chamberadjacent one end thereof through which material to be mixed is charged;a second opening from said mixing chamber adjacent an end opposite fromsaid first opening through which mixed material is discharged; a firstscrew portion on each of said bladed rotors adjacent said first openingadapted to advance material to the central bladed portion; a secondscrew portion on each of said bladed rotors adjacent an opposite end ofthe rotor from the first screw portion and adjacent said second opening,said second screw portions having substantial peripheral clearancerelative to a surrounding chamber portion; structure forming a materialreceiving conduit, at least a portion of which is cylindrical, incommunication with said discharge opening for receiving materialadvanced under pressure through the mixing chamber and second opening,and having a discharge end and an extrusion die at said end; a rotatablescrew extending axially in said receiving conduit closely receivedwithin the cylindrical portion and extending substantially the lengththereof to restrict flow of material from the mixing chamber into andthrough the conduit and constructed to further condition said materialthrough rotation of said screw; means to rotate said screw at acontrolled rate to convey material away from said second opening of themixing chamber and to force said material axially along the conduit andthrough said extrusion die.
 7. In a method of continuously mixingmaterial such as rubber, plastics, and the like, the steps comprising:introducing material to be mixed into a mixing chamber and adjacent oneend of a pair of adjacent generally coextensive rotors each havingbladed portions twisting in opposite directions, rotating the rotors inopposite directions to mix the material, continuously advancing thematerial along the rotors toward a discharge passageway from the mixingchamber, restricting movement of material through the dischargepassageway by a material moving means offset from the axes of the rotorsand operative to positively convey material from the dischargepassageway, sensing pressure within the mixing chamber, and varying thespeed of said material moving means to maintain optimum pressure in themixing chamber.
 8. In a method of continuously mixing material such asrubber, plastics, and the like, the steps comprising: introducingmaterial to be mixed into a mixing chamber and adjacent one end of apair of adjacent generally coextensive rotors each having blade portionsthat are oriented more lengthwise of their axis of rotation thancircumferentially and twist in opposite directions, rotating the rotorsin opposite directions to mix the material, continuously advancing thematerial along the rotors into a conduit in an extruder housing whichconduit is connected with the mixing chamber and is radially offset fromand extends transversely of the axis of the rotors, controlling the rateof flow of material from the mixing chamber by controlling thethroughput of the extruder by varying the speed of rotation of anextruder screw in the conduit, and circulating a heat exchange fluidthrough passages in the walls of the mixing chamber and extruder housingto control the temperature of material being mixed.
 9. In a method ofcontinuously mixing material such as rubber, plastics, and the like, thesteps comprising: introducing material to be mixed into a mixing chamberand adjacent one end of a pair of adjacent generally coextensive rotors,rotating the rotors to mix the materials, advising the material underpressure along the rotors toward a discharge passageway from the mixingchamber, restricting movement of material through the dischargepassageway while concurrently and positively conveying incrementalportions of material from the discharge passageway, sensing thetemperature of the material advanced from the mixing chamber andestablishing a desired temperature by changing the rate at whichmaterial is conveyed from the discharge passageway.
 10. In a continuousinternal mixer: a structure forming a mixing chamber having twointerconnected substantially cylindrical parallel portions; two rotors,one supported by bearings adjacent opposite ends thereof for rotation ineach cylindrical portion of the mixing chamber and each having in themixing chamber a central portion with blade portions oriented morelengthwise of the axis of the rotor than circumferentially thereof andtwisting in opposite directions less than 180* about the axis of therotor to mix material in the mixing chamber; each of said blade portionshaving convex leading surfaces; said oppositely twisting blade portionsof each rotor extending inwardly from adjacent opposite ends of themixing chamber toward the center of the rotor in generally helicalpaths; means for rotating said rotors in opposite directions; a firstopening to said mixing chamber adjacent one end thereof through whichmaterial to be mixed is charged and a second opening from said mixingchamber adjacent an end opposite from said first opening through whichmixed material is discharged; said second opening being located betweensaid bearings; a screw portion on each of said rotors adjacent saidfirst opening adapted to advance material to the central bladed portionof said rotors; structure forming a material receiving conduit, at leasta portion of which is cylindrical, in communication with said secondopening and radially offset from and extending transversely of the axesof the rotors for receiving material from said mixing chamber; passagesin the structure forming said mixing chamber for the circulation of heatexchange meDium therethrough; passages in the structure forming saidmaterial receiving conduit for the circulation of heat mediumtherethrough; a rotatable screw extending axially in said receivingconduit closely received within the cylindrical portion to control theflow of material from the mixing chamber into and through said conduit;and means to rotate said screw at a controlled rate to convey materialaway from said discharge opening.
 11. In a continuous internal mixer; astructure forming mixing chamber having two interconnected substantiallycylindrical parallel portions; two rotors, one supported for rotation ineach cylindrical portion of the mixing chamber and each having in themixing chamber blade portions that twist in opposite directions lessthan 180* about the axis of the rotor to mix material in the mixingchamber; means for rotating said rotors in opposite directions; a firstopening to said mixing chamber adjacent one end thereof through whichmaterial to be mixed is charged and a second opening from said mixingchamber adjacent an end opposite from said first opening through whichmixed material is discharged; a first screw portion on each of saidrotors adjacent said first opening adapted to advance material to thecentral bladed portion of said rotors; a second screw portion on each ofsaid rotors adjacent an opposite end of the rotor from the first screwportion and adjacent said second opening, said second screw portionhaving substantial peripheral clearance relative to a surroundingchamber portion; structure forming a material receiving conduit, atleast a portion of which is cylindrical, in communication with saiddischarge opening and offset from and extending transversely of the axesof the rotors for receiving material from said mixing chamber; passagesin the structure forming said mixing chamber for the circulation of heatexchange medium therethrough; passages in the structure forming saidmaterial receiving conduit for the circulation of heat mediumtherethrough; a rotatable screw extending axially in said receivingconduit closely received within the cylindrical portion to control theflow of material from the mixing chamber into and through said conduit;and means to rotate said screw at a controlled rate to convey materialaway from said discharge opening.
 12. In a continuous internal mixer: astructure forming mixing chamber having two interconnected substantiallycylindrical parallel portions; two rotors, one rotatable in eachcylindrical portion of the mixing chamber and having blade portions thattwist in opposite directions to their axes of rotation for mixingmaterial in said mixing chamber; means forming a first opening to saidmixing chamber adjacent one end thereof through which material to bemixed is charged; a second opening from said mixing chamber adjacent tothe end thereof remote from said first opening through which mixedmaterial is discharged; means supporting said structure and said rotorsfor relative movement axially of said rotors; means for rotating saidrotors in opposite directions; means forming a material receivingconduit in communication with said second opening and offset from theaxes of said rotors; a rotatable screw extending axially in saidreceiving conduit to control the flow of material from said mixingchamber into and through said conduit; and means to rotate said screw ata controlled rate.
 13. In a continuous internal mixer: a structureforming mixing chamber having two interconnected substantiallycylindrical parallel portions; two rotors, one rotatable in eachcylindrical portion of the mixing chamber and having blade portions thattwist in opposite directions to their axes of rotation for mixingmaterial in said mixing chamber; a first opening to said mixing chamberadjacent one end thereof through which material to be mixed is charged;a second opening from said mixing chamber adjacent to the end thereofremote from said first opening through which mixed material isdischarGed; means supporting said structure and said rotors for relativemovement axially of said rotors; means connected to the ends of saidrotors remote from said first opening for rotating said rotors inopposite directions; means forming a material receiving conduit incommunication with said second opening and offset from the axes of saidrotors; a rotatable screw extending axially in said receiving conduit tocontrol the flow of material from said mixing chamber into and throughsaid conduit; and means to rotate said screw at a controlled rate. 14.In a continuous internal mixer: a structure forming mixing chamberhaving two interconnected substantially cylindrical parallel portionsand a material inlet opening adjacent to one end of the chamber; tworotors one rotatable in each cylindrical portion of the mixing chamberand having blade portions in said cylindrical portions of said mixingchamber that twist in opposite directions to their axes of rotation formixing material in said mixing chamber; a material discharge openingadjacent to the end of said mixing chamber remote from said inletopening through which mixed material is discharged; means supportingsaid structure for movement axially of said rotors; and means connectedto the ends of said rotors remote from said first opening for rotatingsaid rotors in opposite directions; means forming a material receivingconduit in communication with said discharge opening and offset from theaxes of the rotors; a rotatable screw extending axially in saidreceiving conduit to control the flow of material from the mixingchamber into and through the conduit; and means to rotate said screw ata controlled rate.
 15. In a continuous internal mixer: a structureforming mixing chamber having two interconnected substantiallycylindrical parallel portions; two rotors, one rotatable in eachcylindrical portion of the mixing chamber and having blade portions thattwist in opposite directions to their axes of rotation for mixingmaterial in said mixing chamber; a first opening to said mixing chamberadjacent one end thereof through which material to be mixed is charge; asecond opening from said mixing chamber adjacent to the end thereofremote from said first opening through which mixed material isdischarged; means supporting said structure and said rotors for relativemovement axially of said rotors; drive means for rotating said rotors inopposite directions; means stationary with respect to said drive meansforming a material receiving conduit in communication with said secondopening and offset from the axes of said rotors; a rotatable screwextending axially in said receiving conduit to control the flow ofmaterial from said mixing chamber into and through said conduit; andmeans to rotate said screw at a controlled rate.
 16. In a continuousinternal mixer: structure forming a mixing chamber having a materialfeeding opening adjacent one end; a rotor supported by bearings adjacentopposite ends thereof for rotation in said mixing chamber and having inthe mixing chamber a central portion with blade portions orientated morelengthwise of the axis of the rotor than circumferentially thereof andtwisting in opposite directions less than 180* about the axis of therotor for mixing material in said mixing chamber; each of said bladeportions having convex leading surfaces; said oppositely twisting bladeportions extending inwardly from adjacent opposite ends of the mixingchamber toward the center of the rotor in generally helical paths, meansfor rotating said rotor at a controlled speed; structure forming amaterial conveying conduit, at least a portion of which is cylindrical,adjacent the end of said mixing chamber opposite said material receivingopening in communication with the mixing chamber at a location betweensaid bearings and radially offset from and extending transversely of theaxis of said mixing chamber; said structure forming said mixing chamberhaving passageways therein for the circulation of heaT exchange mediumclosely adjacent the interior wall of said mixing chamber; saidstructure forming said conduit having passageways therein for thecirculation of heat exchange medium closely adjacent the interior wallof said conduit; a rotatable screw extending axially in said conduitclosely received in the cylindrical portion to control flow of materialfrom the mixing chamber into and through the conduit, said screw beingrotatably supported in said conduit with its axis offset from the axisof said rotor; and means to rotate said screw at a controlled speed toconvey material away from the mixing chamber.
 17. In a continuousinternal mixer: structure forming a mixing chamber; a bladed rotorsupported for rotation in said mixing chamber and having in the mixingchamber first and second pairs of blade portions each having a convexleading surface and each pair extending in generally opposite helicalpaths more lengthwise than circumferentially of the axis of the rotorfrom opposite ends of the mixing chamber toward the center thereof; saidmixing chamber having an opening adjacent one end through which materialto be mixed is fed thereto; a double-thread screw feed portion on saidrotor in advance of said blade portions; each of said double threads ofsaid screw feed portion terminating at and connected with one of saidpair of blade portions adjacent said screw feed; structure forming amaterial receiving conduit extending transversely of said mixing chamberand in communication with the end of said mixing chamber opposite saidopening through which material is fed thereto for receiving mixedmaterial from said mixing chamber; a rotatable screw in said receivingconduit with its axis offset from the axis of said rotor for controllingflow of material from the mixing chamber into and through said conduit;and means to rotate said screw.
 18. In a method of continuously mixingmaterials such as rubber, plastics, and the like, the steps comprising:introducing material to be mixed into one end of a mixing chamber andadjacent one end of a pair of adjacent generally coextensive rotorsrotatable therein and each having first and second pairs of blades, eachhaving a convex leading surface and each pair extending in generallyopposite helical paths more lengthwise than circumferentially of theaxis of the rotors from opposite ends of the mixing chamber towards thecenter thereof, the blades of each pair being displaced from one anotherabout 180* circumferentially of the rotor and the blades of one pairbeing displaced circumferentially about the rotor from the other pairwith adjacent ends overlapping; rotating the rotors in oppositedirections to mix the material and advance it along the rotors to ascrew in a conduit communicating with the end of the mixing chamberopposite the end into which the material is introduced and offset fromand extends transversely to the axes of the rotors; controlling the rateof flow of material from the mixing chamber by controlling the speed ofrotation of the screw, and circulating a heat exchange fluid throughpassages in the walls of the mixing chamber and the screw housing tocontrol the temperature of material being mixed.